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Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Canyon and 2010 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

Dimmer Switch Malfunction

  1. Ignition OFF, disconnect the headlamp and panel dimmer switch connector.
  2. Ignition OFF, verify that a test lamp illuminates between the low reference circuit terminal 3 and B+.
    • If the test lamp does not illuminate, test the low reference circuit for an open/high resistance.
  3. Ignition ON, verify that the scan tool Dimming Potentiometer parameter displays greater than 4 V.
    • If the parameter displays less than the specified value, test the switch signal circuit for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3 A fused jumper wire between the signal circuit terminal 14 and the low reference circuit terminal 3. Verify the scan tool Dimming Potentiometer parameter displays less than 1 V.
    • If the parameter displays greater than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If the circuits test normal, test or replace the headlamp and panel dimmer switch.

Interior Backlighting Malfunction

    NOTE: Each interior backlighting component may need to be disconnected to isolate a short to voltage or short to ground. Use the schematic to identify the following:
    • Backlighting components the vehicle is equipped with.
    • Component locations on the backlighting control circuit
    • Each component's control and ground circuit terminals
  1. Ignition OFF, disconnect the harness connector at any component with inoperative backlighting.
  2. Ignition OFF, scan tool disconnected, interior lamps OFF, doors CLOSED, test for less than 5 Ω between the ground circuit and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the control circuit and ground.
  4. Command the Gauge LED dimming ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the component with inoperative backlighting.
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